The invention relates to a memory device, including a plate of magnetic material for storing digital information in the form of magnetic domains, a main magnetic field generator for sustaining the domains by means of a bias magnetic field which is directed approximately transversely of the plate, and a rotary magnetic field generator for driving the domains along a domain guide structure which comprises discrete, magnetic elements. At least one discrete magnetic element is connected as a domain detection element by being connected to an output of a detection current generator. The domain detection element includes a series of magnetic and electrically series-connected, at least substantially chevron-shaped elements. The detection element is connected to an input of a pick-up element. A device of this kind is known from the article by A. H. Bobeck et al., Evolution of Bubble Circuits Processed by a Single Mask Level, IEEE Transactions on Magnetics, Vol. MAG 9, September 1973, pages 474 ff. FIG. 3 of this article shows a number of detector configurations. The detector element consists of a series of chevrons (of permalloy), successive chevrons being electrically connected either at their centers, or at alternating ends, or at the centres of alternating chevron legs, i.e. the portions situated between the center and an end. The detection elements form part of a domain guide structure. A rotary magnetic field which rotates in the plane of the plate drives the domains in a direction which is transversely to the symmetry axis of the chevrons. When a domain passes the detection element, a detection signal is supplied as a result of a magneto-resistance effect under the influence of the rotary magnetic field and the presence or absence of a domain.
Configurations of this kind have the advantage that they may be composed of a single layer of material having a suitable magneto-resistive effect as well as a suitable electrical conductivity. They have a further advantage in that the sensitivity of the detection element can be increased by the use of a larger number of chevrons; a passing domain expands further, but continues to exhibit coherence. Detection elements of this kind have the drawback that two signals are supplied with a mutual phase difference of approximately 180.degree. (related to one period of the rotary magnetic field), both signals being determined by magnetoresistance variation and also being determined in approximately the same manner by the possibly present domain. Moreover, the domain-determined part of the signal is influenced by the data rate and is notably reduced if two domains are presented to the detection element in directly successive periods of the rotary magnetic field. The signal-to-noise ratio may thus be inadmissibly reduced. The problem can be solved by separating two domains or two information-carrying domain positions (full or void) each time by an information-less void period, but the bit data rate is then substantially halved.